Lecturers have threatened strikes if their demands are not met. Photograph: Luke Macgregor/Reuters

Lecturers at half of the country's universities will work to rule this week in a bitter dispute over their pensions.

From Monday, academics at 67 universities – including Oxford, Cambridge and Imperial College London – will only work their contracted hours, refuse to cover for colleagues and skip meetings in protest at changes which they argue will leave them with less in retirement.

They have threatened to carry out rolling strikes and boycott the marking of students' work unless employers make the changes they demand. More than 40,000 lecturers could take part in the action, potentially affecting more than a million students.

Employers want to change the lecturers' pension scheme – the Universities Superannuation Scheme (USS) – to put new members on career-average, rather than final salary, pensions.

They would like to introduce a normal pension age of 65, for service from the 1 October, although existing members over the age of 55 would be exempt from the change to the pension age.

Currently, members pay 6.35% of their salary into the scheme and employers pay 16% of the value of members' salaries.

Under the changes, the employee contribution rate for members of the final salary scheme would increase to 7.5%, while those on the new career average scheme would pay 6.5%. Pension increases would be "inflation-proofed" in line with increases in the Consumer Prices Index (CPI), subject to a maximum increase of 10%.

The lecturers' trade union, the University and College Union (UCU) says the average lecturer could lose more than £100,000 during retirement as a result of the change.

The pension scheme is one the biggest occupational pension schemes in the UK. In the 12 months to March 2010, USS grew by £4.5bn despite a significant economic downturn, in what was described as a "good investment performance" by the fund's managers.

UCU says that, in two referendums, 90% of those who belonged to the scheme have voted against the changes to their pensions. Some 77% backed sustained industrial action, the union says.

Sally Hunt, general secretary of UCU, says that employers have refused to talk to the union: "We cannot negotiate with an empty chair. We are keen to resolve this dispute as quickly as possible with minimal disruption and hope those universities keen to avoid unnecessary confrontation and disruption will start to apply pressure on those refusing to talk."